RESULTS: 2136 patients were treated in 4 years, and 65 patients acquired nonsocial infection with the infection rate of 3.04%. The top three infection sites were respiratory tract, urinary tract and gastrointestinal tract, and the infection rates were 45.84%, 22.22% and 12.50%, respectively. 68 pathogens were isolated, with 44 stains of gram negative bacteria (64.71%), 15 stains of gram positive bacteria (22.06%) and 9 stains of fungi (13.24%). Among them, the infection rate of Antibacterial Badman was the highest (32.35%). There were seven risk factors of nonsocial infection, including, elderly (over 65 years), once infection in the previous 3 months, white blood cell count decreased (<1.5*109/L), longer hospitalization days (equal to or more than 30 days), broad-spectrum antibiotic use for a long time (more than or equal to 7 days), recently received immunosuppressive therapy and the patients underwent invasive operation, respectively. Hospitalization days were equal to or more than 30 days with the maximum OR value (19.069), which was the main influence factor for the nonsocial infection.